Translation:Language is an instrument for thought.
It's because broad and/or abstract concepts are most often in the definite form in Norwegian. It seems strange to native English speakers because we don't use the definite form that way. (I don't mean to assume that you are one, but it could be a possible explanation if you're confused by the use of the definite form.) Take for example 'life', which is obviously a broad and pretty abstract concept - in Norwegian, it's referred to in the definite form as 'livet'. Like, 'livet er sånn' - 'life is like that'.